Why Gene Therapy Reimbursement Takes So Long: The Float
Gene therapy reimbursement takes so long because a payer's "yes" and a payer's payment are two different events, sometimes separated by a year. The insurer approves coverage, the hospital buys the million-dollar product and treats the patient, and then the money doesn't arrive for months. In the meantime the hospital is carrying the cost. Bambi Grilley, President-Elect of the International Society for Cell and Gene Therapy (ISCT), calls that gap a float, and in her Open Door Salon conversation with ISCT Chief Medical Officer Jaap Jan Boelens, she explained why it is bigger than a billing nuisance.
Why doesn't an insurer's "yes" mean the hospital gets paid?
Because approval to reimburse and the act of reimbursing are separate steps, and only the first one happens quickly. A coverage decision tells the hospital the claim will eventually be honored. It does not move any money. Grilley is careful to separate the two, because conflating them is exactly how the problem stays invisible.
Not only the decision that an insurance company would theoretically reimburse, but the actual process of actually reimbursing.
That distinction is the whole story. The coverage question, whether insurance will pay at all, is covered in why insurance won't cover gene therapy. This is the step after that: the payer has agreed, and the cash still hasn't shown up.
What is the million-dollar float?
It is the money a hospital has already spent on a therapy it hasn't been paid back for, and for gene therapy it runs to seven figures per patient. Grilley described the pattern she keeps hearing from centers.
The insurance company said they would pay. The hospital has invested in buying the product for the patient. The patient may have actually received the product by now. And the reimbursement is months, sometimes even, I've heard, as long as a year later, not been paid. That's a big float if you're looking at a product that costs a million dollars, plus hospital charges.
Put plainly: the institution fronts a million dollars or more, delivers the cure, and then acts as an unpaid lender to the insurer for up to a year. For a large academic medical center that can be absorbed. For a smaller center, it is a reason not to offer the therapy at all, which quietly shrinks the number of places a patient can be treated. The sticker price itself, taken up in why cell and gene therapy is so expensive, is only part of the pressure; the timing is what strands the balance sheet.
Why is a payment delay an existential problem, not just a cash-flow one?
Because a therapy that hospitals can't afford to float is a therapy that doesn't reach patients, and that is the line Grilley draws for the whole field. She frames unsolved reimbursement as an existential threat to cell and gene therapy: if the field can't make the products financially viable to deliver, the science stops mattering because no one can afford to use it. The same delay drives the clinical decision in why patients walk away from a cure over single-case agreements, and it is why an approved product can still be, in practice, unavailable to patients.
What breaks when hospitals can't carry the float?
The list of centers willing to treat these patients gets shorter, and access narrows to the largest institutions. A therapy is only as available as the network of hospitals that can afford to deliver it and wait to be paid. When the float is a year on a million-dollar product, the calculation pushes treatment toward a handful of well-capitalized centers and away from the smaller sites that patients can actually reach. That is how a reimbursement process problem becomes an access problem, without anyone denying a single claim.
The fix, in Grilley's framing, isn't more approvals or lower prices alone. It is closing the gap between the payer's decision and the payer's payment, so a hospital isn't penalized for curing someone. The delivery model itself may change eventually, though on ISCT's own read in vivo gene therapy is still a decade-plus problem. Sponsors and health systems working on that problem can partner with Open Door Salon or follow the field's own work at ISCT.
Drawn from the recorded, on-the-record Open Door Salon conversation with Bambi Grilley and Jaap Jan Boelens of ISCT. For context on how novel gene therapies are reimbursed under US coverage rules, see CMS coverage and payment resources.